1. Field of the Invention
This invention relates to fluidized bed coal gasification reactors, and more particularly to arrangements for feeding fluid, including particulate mediums, into the reactor.
2. Description of the Prior Art
One of the most promising forms of energy utilization is gasification of coal. A particularly promising approach in the use of fluidized beds in the gasification process, for example, as discussed in U.S. Pat. Nos. 3,804,606 and 3,847,563.
Among the mediums fed into the fluidized bed reactors are solid combustibles in a transport gas, a combustion gas, and a fluidizing gas which can be used in addition to the other gases for fluidization. The solid combustibles include char fines, coke or pulverized coal, carried into the reactor by a transport gas which can include steam, air, nitrogen, carbon dioxide or recycled product gas. The combustion gas is typically oxygen or air and the fluidizing gas can include steam or recycle gas which also assists in the combustion process.
In the prior art, air and steam have typically been injected into the reactor vessel either radially or axially through a central tube. The solid combustibles, such as char fines, have been directed radially, from the side of the reactor vessel, into the fluidized bed, or vertically from the upper portions of the reactor vessel. Additionally, separate sparger rings have been utilized to increase fluidization in selected areas, particularly the lower regions of the bed. Ash is removed from the lower end of the reactor, and a product gas is discharged at the upper end.
While these arrangements achieve desired gasification, improvements can be made. For example, the prior art systems are subject to plugging at the ash exit by large, two to ten inch diameter clinker-type material formed from a defluidized zone at the air tube outlet or by slugging, the formation of excessively large bubbles causing an exchange of hot and cold particles in the upper section of the reactor bed. Additionally, the effect of radial impingement of the solid combustibles and transport gas upon the combustion jet can influence the length and shape of the jet resulting in undesirable clinker formation and potential plugging of the discharge system. An auxiliary fluidizing means in addition to, or alternative to, the sparger rings, can be desirable to assure sufficient mixing of the particles and recirculation of the solids in the zone of the combustion jet.
It is therefore desirable to provide configurations for feeding the reactant mediums into the fluidized bed reactor vessel which improve upon prior systems.